Electron Beam Welding

Electron Beam Welding (EBW) is a fusion joining process that produces a weld by impinging a beam of high energy electrons to heat the weld joint. Electrons are elementary atomic particles characterized by a negative charge and an extremely small mass. Raising electrons to a high energy state by accelerating them to roughly 30 to 70 percent of the speed of light provides the energy to heat the weld.

An EBW gun functions similarly to a TV picture tube. The major difference is that a TV picture tube continuously scans the surface of a luminescent screen using a low intensity electron beam to produce a picture. An EBW gun uses a high intensity electron beam to target a weld joint. The weld joint converts the electron beam to the heat input required to make a fusion weld.

The electron beam is always generated in a high vacuum. The use of specially designed orifices separating a series of chambers at various levels of vacuum permits welding in medium and nonvacuum conditions. Although, high vacuum welding will provide maximum purity and high depth to width ratio welds.

EBW Benefits

• Single pass welding of thick joints

• Hermetic seals of components retaining a vacuum

• Low distortion

• Low contamination in vacuum

• Weld zone is narrow

• Heat affected zone is narrow

• Dissimilar metal welds of some metals

• Uses no filler metal

EBW Limitations

• High equipment cost

• Work chamber size constraints

• Time delay when welding in vacuum

• High weld preparation costs
• X-rays produced during welding
• Rapid solidification rates can cause cracking in some materials

EBW Problems and Discontinuities

• Undercutting

• Porosity

• Cracking

• Underfill

• Lack of fusion

• Shrinkage voids

• Missed joints

*************************************************************************************